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To forum, help me please.

Have a question.
I notice that on 20m the power output drops dramatically (~50%).
Necessary fine-tune the LP filter?
Or are other problems: eg. DDS-VFO?
TKS Francesco, HB9AFZ

On 21/06/2013 14:33, cecco.delprete wrote:

I notice that on 20m the power output drops dramatically (~50%).

Hi Francesco

I noted a drop in power after 10MHz in my tests but didn't worry about it, not 50% at 14MHz but a full drop 50% at 18MHz which the rises to give more power on 28MHz. It is a simple design, not optimised for any band, QRP, and after all its only a 3dB drop.

Necessary fine-tune the LP filter?

I don't think you do do anything to optimise the LPF.

Or are other problems: eg. DDS-VFO?

Have you got results above 14MHz, adjustment of the blue Mark Space adjustment pot is quite critical, I find adjusting for max RF power out to the antenna on 28MHz is as good as anything.

73 Eddie

Do you mean that it starts high and then a few seconds later it drops ?

Or do you mean that the higher the frequency = lower output ?

With 3x BS170 @ 9v you will typically see:-

1.1w to 24Mhz
650mw @ 21Mhz
250mw @ 28Mhz (50mw @ 5v ?)

This is normal.

73 de Andy